It is well known that where a jet-propelled missile is powered by an air-breathing jet engine, an air inlet duct must be provided to supply the engine with a requisite amount of compressed-air energy. These missiles are generally launched from a container or canister which protects the missile during shipping and handling and also acts as a guide during the initial flight phase of the missile. The cylindrical cross section of the canister requires that any wings, fins or ducts not project beyond the missile contour until the missile is in flight.
A variety of movable, folding or collapsible air inlet ducts have been used in the past, as evidenced by, for example, U.S. Pat. No. 4,221,230 to Nicoloff et al. (1990); U.S. Pat. No. 3,659,424 to Polk, Jr. (1972); U.S. Pat. No. 4,121,606 to Holland et al. (1978); U.S. Pat. No. 4,418,879 to Vanderleest (1983); U.S. Pat. No. 4,307,743 to Dunn (1981); U.S. Pat. No. 5,301,901 to Kutschenreuter, Jr. (1994); U.S. Pat. No. 4,620,679 to Karanian (1986); and U.S. Pat. No. 4,655,413 to Genssler et al. (1987). While effective in many applications, the prior art deployable air inlet ducts tend to be mechanically complex and heavy, they frequently occupy an undesirable large portion of the internal vehicle volume, and since these ducts often are not flush with the missile's outer body when in the stowed position, they typically cause considerable drag at high speeds. Prior art air inlet ducts also utilize various hinges and linkages to enable movement of the air inlet duct from the stowed to the deployed positions. In addition, the prior art has taught the movement of the air inlet duct by a mechanical or hydraulic actuator responsive to a computer-initiated signal that deploys the duct along its hinges or linkages to an optimum extended position.
It would be desirable to provide a lightweight, simple, aerodynamically clean and inexpensive self-deploying air inlet duct in which movement between the deployed and stowed positions would be obtained at a predetermined time without the necessity for complicated hinges, links and actuators.